This invention refers to a centrifugal device for clamping spools on rapidly rotating spindles, and in particular to a clamping device which can be applied to the spindles of textile machines. Spools are currently clamped onto the spindles of textile machines by means of mechanical locking systems which include the use of manually operated plugs engaging and disengaging the spool and the spindle itself. The manual operation of fitting and removing the locking plug is a lengthy and dangerous operation to carry out, in that it must be carried out with the spindle completely stationary; moreover, with this system, it is not possible to doff the spools automatically.
The European published patent application No. 0078978 refers to a spoolholder operated by fluid under pressure, which makes use of at least two elastomeric spool clamping elements, arranged along a spindle; each clamping element comprises an annular shank portion and a conical disk portion having a cylindrical outer edge which is axially compressed by fluid actuated urging means surrounding the disk portion in order to expand it, causing the cylindrical edge surface of the conical portion to radially press and adhere to the inner surface of the spool, holding the latter on the rotating spindle.
This known clamping device has been proposed in place of expansible metal disk-like clamping devices which could damage the spools. Even though it is possible to automatically lock the spools, with the device according to European published patent application No. 0078978, it nevertheless suffers from numerous drawbacks which make it rather unsuitable for use on spindles which are made to rotate at very high speed, over 15,000/20,000 revolutions a minute, or for clamping very heavy spools. In particular, in the clamping device according to the above European patent application, the internal surface of the spool is subjected merely to radial clamping forces, due to the simple axial compression of the outer edge of the conical disk portion. Consequently, if the axial compression of the conical portion were to weaken or accidentally decrease, then the spool would no longer be securely clamped and could slide off the rapidly rotating spindle, due to axial components of the forces which could come into play. Moreover, the elastomeric retaining element is shaped in such a way as not to exclude the danger of it breaking and becoming detached from the spindle; for these reasons, it is desirable to prevent excessive radial expansion and bending of the conical disk portion of each elastomeric spool clamping element. This invention concerns a device for clamping spools on spindles which, unlike the conventional approaches, actually exploits the effect of the centrifugal force itself to clamp the spool onto a rapidly rotating spindle, exerting an axial thrust along the spool, which tends to hold the spool locked against a stop shoulder on the spindle.
A further scope of this invention is to provide a clamping device, as hereinbefore described, which makes use of elastomeric retaining elements which are specially designed to provide a clamping force which gradually increases with the number of revolutions of the spindle.
A further scope of the invention is to provide a clamping device which can easily be applied to any type of spindle whatsoever, which is extremely reliable, and not liable to accidentally break or come loose, in that it is provided with retaining means which prevent it from sliding axially off the spindle.